Input devices including proximity sensor devices (also commonly called touchpads or touch sensor devices) are widely used in a variety of electronic systems. Input devices also include fingerprint sensors and other biometric sensor devices. A sensor device typically includes a sensing region, often demarked by a surface, in which the sensor device determines the presence, location, motion, and/or features of one or more input objects. Sensor devices may be used to provide interfaces for an electronic system. For example, sensor devices are often used as input devices for larger computing systems (such as opaque touchpads and fingerprint sensors integrated in, or peripheral to, notebook or desktop computers). Sensor devices are also often used in smaller computing systems (such as touch screens integrated in cellular phones).
Many sensor devices utilize capacitive sensing principles in order to detect the input object. Capacitive sensors, including those based on trans-capacitance, provide several advantages over other sensing technologies. However, capacitively sensing fingerprint features and other fine features is a challenging task. While existing sensors can provide adequate performance, they often suffer from low signal quality. Improving the signal quality can provide several benefits, such as more accurate biometric matching and increased flexibility in integrating the sensor in a variety of applications, e.g., those with thicker cover layers over the capacitive sensor.